In recent years, SNSs (Social Networking Services) have rapidly spread, and are widely used. Further, information is actively shared between individuals through such an infrastructure. Hence, in addition to a conventional mode of sharing information by sending and receiving messages such as electronic mails on 1-to-1 basis, a mode (e.g. an SNS) of sharing information by allowing specific or non-specific people to browse messages posted by individuals is widely used.
Managing who to disclose information to share becomes difficult as the amount of the information and the number of parties to share information with increase. This is because individuals have difficulty in paying thorough attention to an information share state. As a result, a risk that personal information may be unintentionally leaked increases. That is, a likelihood that basic information such as an address, a name and a date of birth, and various pieces of information such as the faith, the hobbies, tastes, behavior history and personal relationships may be unintentionally leaked through information sharing means such as an SNS has increased more than ever.
Multiple SNSs provide means for setting an information disclosure range to prevent such a leakage of personal information from occurring. For example, Facebook (registered trademark) makes it possible to set a release range to “only me”, “specific people or list of people”, “friends”, “friends of friends” and “release” per each message. Thus, it is possible to disclose highly confidential information to only specific parties.
Usually, this information disclosure range is set statically by a user. By, for example, setting per each message who to disclose information to upon posting a message, the user can manage how to share information in message units.
Patent Literature 1 to 5 discloses techniques for setting or changing a range for disclosing information to other people as related techniques.
Patent Literature 1 discloses a file management system whose object is to specify a change in a storage medium which stores information or a whereabouts of a person, and prevents an operation leading to leakage of information from being performed in advance. The file management system according to Patent Literature 1 prevents an operation which is highly likely to lead to leakage of information beyond a share range by setting the share range to information such as disperse files under management of an organization according to a value of the information.
In addition, the file management system according to Patent Literature 1 sets execution conditions in label units per operation which is highly likely to lead to leakage of information by setting as a label a combination of a category indicating a type of information, and a confidential level. Further, the file management system includes a policy list in which the execution conditions and a share destination are set. The file management system sets a file share range by allocating a label to a file instead of directly allocating a policy to the file.
Patent Literature 2 discloses a social network information managing method and social network information management system whose object is to manage as connection information a history that people actually have met at a specific place and share and effectively utilize personal connection information. The management system according to Patent Literature 2 generates the connection information by analyzing and collecting interaction status information and personal attribute information detected when people form a community through an interaction.
In addition, the social network information management system according to Patent Literature 2 detects a personal attribute ID of a person who interacts with another person in a specific area, and an interaction period, and generates interaction status information including an area ID, an interaction period and a personal attribute ID. The management system collects and filters this interaction status information, and creates real community information. Next, the management system calculates a connection level from this real community information, generates connection information and provides the connection information for retrieval of the connection information.
Patent Literature 3 discloses a communication control apparatus of a Weblog system which preferentially presents communication information from a user who frequently performs communication while making a Weblog site open, and excludes unilateral information such as spams. This communication apparatus extracts a communication relationship between users from a history of communication activities which makes it possible to specify a user on a website in the Weblog system which encourages communication between users through comments and trackbacks given to a general Weblog site operated by a user. Further, the communication control apparatus calculates an inter-user distance value which takes a lower value when a communication activity is frequent (the number of times and the frequency) and a bidirectionality (comments, advertisement and trackbacks are given from both users) are higher, and controls content/display order or the like of communication information which is presented to a user according to this distance value.
The communication control apparatus according to Patent Literature 3 counts frequencies or the like of communication activities performed on a Weblog site, and specifies a user closer to a given user from an inter-user distance value calculated based on the frequencies. Consequently, the communication control apparatus can preferentially present information related to communication which a user more frequently performs bidirectionally while basically generating a fully open system like the current Weblog service. Further, the communication control apparatus can exclude unilateral information such as spams.
Patent Literature 4 discloses a social network electronic mail filtering method. This method includes the following steps. First, the method specifies a first electronic mail address whose distance from a user is 0 degree in a social network. Next, the method associates the first electronic mail address with a first trust level. Next, the method specifies a second electronic mail address whose distance from the user is 1 degree in the social network. Further, the method associates the second electronic mail address with a second trust level. According to the above method, it is possible to filter an electronic mail message based on the social network.
Patent Literature 5 discloses a server which deletes profile information of a user from an address book of a mobile terminal apparatus of another user according to a frequency of communication.